Method of dissolving sulfur from ores



METHOD OF DISSOIJVING' SULPHUR FROM ORES G. w. TWEE DDALE Filed March16, 1944 IN VEIV I GR.

ATTORNEY Patented Oct. 15, 1946 UNITED STATES PATENT OFFICET 2,409,408METHOD OFDISSOLVING SULFUR FROM ones George W. Tweeddale, Glendale,Calif.

Application March 16, 1944, Serial No. 526,767

1 Claim. 1

. This invention relates to the extraction of sulfur from free sulfurores by a solvent method and provides an alternative method and means tothat illustrated in applicants copending application Serial No. 512,839.

The principal object of this invention is to provide a method and meansfor extracting sulfur from free sulfur bearing ores in which the endproduct of the extraction will be commercially pure, crystalline sulfur,so that recourse to fur ther purification or refining steps for theremoval of arsenic, and other impurities will be unnecessary.

Other objects of the invention are:

To employ economical, easily available reagents in the process;

To provide a method in which the extraction solvent can be continuouslyreused in a closed circuit with very little loss thereof;

To provide a solvent having a relatively high saturation point so as toobtain maximum recovery from a. minimum of solvent; and

To provide a method and means which will recover substantially all ofthe sulfur content of the ore.

Other objects and advantages reside in the improved solvent and themethod of use thereof. These will become more apparent from thefollowing description of the methods and means employed.

In the following detailed description of the invention reference will behad to the accompanying drawing which forms a part hereof. The drawingillustrates diagrammatically one method of carrying out the improvedprocess.

The solvent employed is a fractionation of petroleum, or a mixture ofpetroleum fractionations, occurring below gasoline and down to andincluding Diesel oil. The preferred solvent is the hydrocarbon known askerosene a commercial mixture of several hydrocarbons more particularlyof the methane series. In fact, hot kerosene forms a highly satisfactorysolvent for dissolving sulfur from its ores without the use of anyadditional reagent or catalyst. The kerosene is heated to approximately140 C. and the ore is either immersed therein or the hot kerosene isflowed through the ore.

The yield can be increased and the time element reduced by combining asecond carbonaceous solvent with kerosene.

It is believed that the second element acts as a catalyst to assist theaction of the kerosene. It appears that any other hydro-carbonfractionation occurring between gasoline and Diesel oil and includingthe latter, will increase the efficiency of the kerosene. However, sincecommercial kerosene is not always a pure fractionation, but. alsocontains more or less of the adjacent fractionations, the catalysts arepresent in the commercial kerosene. Other hydrocarbons, moreparticularly methylated hydrocarbons, appear to increase theeffectiveness of the kerosene.

Kerosene or a mixture of kerosene, with its adjacent fractionations, hasunusually high solvent power for sulfur and will quickly and easilydissolve inexcess of one-third of its weight in sulfur withoutdissolving the arsenic or other impurities contained in the ore. Presentused methods and solvents dissolve not over one-eighth of their Weightin sulfur and produce an impure end product which must be subjected tofurther refining.

In use, the sulfur bearing ore, is ground to approximately one-quartermesh. The ground ore, is either immersed or flooded with boiling solventuntil complete extraction of the sulfur has been obtained. The hot,sulfur-containing solvent is then chilled to a point to causecrystallization of the sulfur to precipitate the latter from thesolution. The loss of solvent is exceedingly low, averaging less than2%. The precipitated crystals have a purity exceeding 99% and contain99% of the sulfur content of the ore. Approximately one pound ofprecipitated crystals will be recovered from two and one-half pounds ofthe solvent provided the latter has reached full saturation. Afterprecipitation the solvent can be immediately reused on the next batch ofore.

One method of employing the improved solvent is illustrateddiagrammatically in the drawing, in which the ore to be treated is fedfrom a chute 25 to a crusher 25 and from thence to a storage bin l3.This method employs a series of filterbottomed cars In traveling on asuitable endless track Ii. These cars may be any of the standard types,arranged to dump their contents either by rotating the car body orhaving a dump bottom therein. The bottom of each car contains a screenor filter plate I 2 of sufiiciently small mesh to prevent the ground orefrom sifting therethrough. The cars are successively filled from thestorage bin l3 and are then forced into a treatment compartment l4. Eachcar that enters the compartment l4 forces the innermost car therefrom toa discharge hopper l5 into which the exhausted ore may be dumped asillustrated. The car then returns to the bin [3 for refilling.

'Spray pipes 56 are supported above the cars adjacent the entrance ofthe compartment l4.

The spray pipes are connected by means of a pressure'pipe I? with a pumpl8 which draws hot solvent from a heater l9 and sprays it upon the orein the cars 52. The solvent percolates downwardly through the ore in thecars, dissolving the sulfur therefrom as it flows, and dischargesthrough the filter bottoms of the cars into a receiver 20. The sprays donot extend over all of the cars so that the innermost cars are allowedto drain their excess solvent into the receiver 20 before they aredischarged from the compartment M.

The solvent with its dissolved sulfur flows to a collector pipe 24thence to a cooling vat 2! where it is chilled in any desired manner,such as by means of refrigerated coils, to a temperature from 30 C. to40 C., to crystalize the sulfur therein. The sulfur settles to thebottom of the cooling vat 2| and may be discharged at intervalstherefrom through any suitable blast gate 22. From the cooling vat thesupernatant sol vent flows to a storage and settling tank 23 from whenceit is drawn to the heater IQ for reuse in the spray pipes I6. The heaterI 9 may be of any desired type suitable for quickly bringing the solventto a temperature of 145 C. or higher. The method could be carried out bysimply immersing the ore in the solvent, but this involves difficultieswhich makes continuous operation impractical.

- claimed and desired secured by Letters Patent is:

A method for recovering sulfur from free sulfur bearing ores comprising:crushing said ore; placing said crushed ore in wheeled cars havingscreened bottoms; forcing each succeeding car beneath a spray of hotkerosene so that it will force the proceeding car from beneath saidspray; collecting the solution flowing from the screened bottoms of saidcars; chilling the collected solution to precipitate the sulfurtherefrom; drawing off the supernatant fluid; heating said latter fluidto approximately C.; returning the heated fluid to said spray; dumpingthe ore from each successive car after it leaves said spray; thencereturning the dumped cars to a position to receive additional crushedore.

GEORGE W. TWEEDDALE.

